KR102517647B1 - Grain-oriented electrical steel sheet manufacturing method and grain-oriented electrical steel sheet - Google Patents

Abstract

A step of obtaining a hot-rolled steel sheet by subjecting a slab containing a predetermined component composition, the balance of which contains Fe and impurities, to obtain a hot-rolled steel sheet; And, a step of subjecting the cold-rolled steel sheet to primary recrystallization annealing including rapid heating with an average heating rate V of 400 ° C. / s or more and imparting a steel sheet tension S, and annealing to the surface of the cold-rolled steel sheet after primary recrystallization annealing A method for producing a grain-oriented electrical steel sheet, comprising a step of applying a separator and then performing flattening annealing.

Description

Grain-oriented electrical steel sheet manufacturing method and grain-oriented electrical steel sheet

The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet.

This application claims priority based on Japanese Patent Application No. 2018-052900 for which it applied to Japan on March 20, 2018, and uses the content here.

A grain-oriented electrical steel sheet is a steel sheet containing about 2% by mass to 5% by mass of Si and highly integrated in the grain orientation of the steel sheet to the {110}<001> orientation referred to as the Goss orientation. Since grain-oriented electrical steel has excellent magnetic properties, it is used, for example, as an iron core material for stationary inductors such as transformers.

The grain orientation of the grain-oriented electrical steel sheet can be controlled by using a catastrophic grain growth phenomenon called secondary recrystallization. In addition, it has been confirmed that by rapidly raising the temperature of the steel sheet in the heating process of the primary recrystallization annealing performed prior to the secondary recrystallization, it is possible to increase the number of Goss-oriented crystal grains having good magnetic properties after the primary recrystallization annealing.

Therefore, in order to improve the magnetic properties of the grain-oriented electrical steel sheet, various rapid temperature raising conditions are being studied in the temperature raising process of the primary recrystallization annealing.

For example, Patent Literature 1 discloses a technology for improving the product quality of a grain-oriented electrical steel sheet by uniformizing the temperature distribution in the sheet width direction of the steel sheet by defining the position of the rapid heating unit in the continuous annealing unit. Patent Literature 2 discloses a technique for suppressing fluctuations in iron loss of a grain-oriented electrical steel sheet by controlling temperature fluctuations inside the steel sheet by controlling the heat pattern and atmosphere in the temperature rising process of primary recrystallization annealing. Patent Literature 3 discloses a technique for strictly controlling the average grain diameter of crystal grains after secondary recrystallization and the deviation angle from an ideal orientation by rapidly heating a steel sheet in primary recrystallization annealing and then rapidly cooling it. Patent Literature 4 discloses a technique for reducing the iron loss of a grain-oriented electrical steel sheet by rapid heating in the temperature rising step of decarburization annealing.

Japanese Unexamined Patent Publication No. 2014-47411 Japanese Unexamined Patent Publication No. 2014-152392 Japanese Unexamined Patent Publication No. 7-268567 Japanese Unexamined Patent Publication No. Hei 10-280041

In the prior art as described above, irregularities (also referred to as wrinkles) may be formed on the surface of the finally obtained grain-oriented electrical steel sheet depending on the conditions of rapid temperature increase in primary recrystallization annealing. Grain-oriented electrical steel sheets having concavo-convex surfaces cause gaps between the steel sheets when laminated, thereby reducing the space factor of the iron core material and degrading the performance of the transformer. In Patent Literature 4, the surface shape of a grain-oriented electrical steel sheet is evaluated, but in the technique described in Patent Literature 4, the occurrence of finer irregularities may not be sufficiently suppressed.

The present invention was made in view of the above problems, and is a novel and improved grain-oriented electrical steel sheet capable of producing a grain-oriented electrical steel sheet with a better surface shape when rapid temperature increase is performed at a higher temperature increase rate than before in primary recrystallization annealing. An object of the present invention is to provide a manufacturing method and a grain-oriented electrical steel sheet manufactured by the manufacturing method. Another object of the present invention is to provide a method for producing a grain oriented electrical steel sheet having a reduced iron loss value even without magnetic domain control treatment, and a grain oriented electrical steel sheet manufactured by the method.

The gist of the present invention is as follows.

[1] A method for manufacturing a grain-oriented electrical steel sheet according to an aspect of the present invention,

Ingredient composition, in mass%,

C: 0.02% or more and 0.10% or less;

Si: 2.5% or more and 4.5% or less;

Mn: 0.01% or more and 0.15% or less;

Sum of S and Se: 0.001% or more and 0.050% or less;

Acid-soluble Al: 0.01% or more and 0.05% or less;

N: 0.002% or more and 0.015% or less

A step of obtaining a hot-rolled steel sheet by heating a slab containing Fe and impurities, the balance of which contains Fe and impurities, at 1280° C. to 1450° C., and performing hot rolling;

A step of obtaining a cold-rolled steel sheet by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing and then performing cold rolling twice or more with intermediate annealing interposed therebetween;

A step of subjecting the cold-rolled steel sheet to primary recrystallization annealing;

Applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, followed by final annealing to obtain a final annealed sheet;

A step of applying a planarization annealing after applying an insulating film to the final annealing plate,

In the temperature raising process of the primary recrystallization annealing, the average temperature increase rate V (℃ / s) in the temperature range of 550 ℃ to 700 ℃ is 400 ℃ / s or more, including the temperature increase in the temperature range of 550 ℃ to 700 ℃ T/L (°C/mm), which is the ratio between the amount of temperature increase T (°C) in the series of temperature increase processes and the heating length L (mm) in the series of temperature increase processes, is 0.1 ≤ T/L ≤ 4.0, and the cold-rolled steel sheet is passed through When the tension S (N/mm2) applied in the direction is 1.96≤S≤(19.6-1.96×T/L) and V≤1000, the tension S is 1.96≤S≤(25.5-0.0137×V), , when V>1000, the tension S is 1.96≤S≤11.8.

[2] A grain-oriented electrical steel sheet according to another aspect of the present invention,

a silicon steel sheet;

A forsterite film disposed on the silicon steel sheet;

an insulating film disposed on the forsterite film;

The silicon steel sheet has a component composition in mass%,

Si: 2.5% or more and 4.5% or less;

Mn: 0.01% or more and 0.15% or less;

Sum of S and Se: 0% or more and 0.005% or less;

Acid soluble Al: 0% or more and 0.01% or less, and

N: 0% or more and 0.005% or less

and the balance includes Fe and impurities,

The average particle diameter of the secondary recrystallized grains of the silicon steel sheet is 10 mm or more and 50 mm or less,

The grain-oriented electrical steel sheet,

The plate thickness is 0.15 mm or more and 0.23 mm or less,

Iron loss Wp is 0.800 W/kg or less with W _17/50 ,

The presence ratio of wrinkles having a steepness of 0.01 or more is 0/m or more and 10/m or less in the sheet width direction,

The magnetic flux density B8 value is 1.930T or more.

According to the above aspect of the present invention, in the case of rapid temperature increase at a higher temperature increase rate than in the prior art in the primary recrystallization annealing, the surface shape is better and the core loss value is reduced even if the magnetic domain control process is not performed. Directional electrons A steel plate and its manufacturing method can be provided.

1 is a diagram showing a specific example of a heat pattern in a temperature rising process of primary recrystallization annealing.
2 is a diagram showing another specific example of a heat pattern in a temperature rising process of primary recrystallization annealing.
3 is a diagram showing another specific example of a heat pattern in a temperature rising process of primary recrystallization annealing.
4 is a diagram showing another specific example of a heat pattern in a temperature rising process of primary recrystallization annealing.
5 is a diagram showing a cross-sectional curve of a grain-oriented electrical steel sheet for explaining a method of obtaining steepness.
6 is a diagram plotting the results shown in Table 1, with the temperature increase rate V taken on the abscissa and the steel sheet tension S taken on the ordinate.
7 is a diagram plotting the results shown in Table 1, with the ratio T/L taken on the abscissa and the steel sheet tension S taken on the ordinate.

EMBODIMENT OF THE INVENTION Below, preferred embodiment of this invention is described in detail, referring an accompanying drawing. However, the present invention is not limited only to the configuration disclosed in the present embodiment, and various changes can be made without departing from the gist of the present invention. Also, in this specification and drawings, components having substantially the same function and structure are assigned the same numbers, thereby omitting redundant description.

The present inventors have obtained the following knowledge as a result of earnestly examining a grain-oriented electrical steel sheet and a manufacturing method of the grain-oriented electrical steel sheet in order to improve the magnetic properties of the grain-oriented electrical steel sheet.

Specifically, in the grain-oriented electrical steel sheet, in the heating process of primary recrystallization annealing, the present inventors rapidly raised the temperature in the temperature range of 550°C to 700°C at an average temperature increase rate of 400°C/s or more, so that after primary recrystallization annealing, magnetic It was found that grains of Goss orientation with good characteristics (also called Goss orientation grains) increased. In addition, the present inventors have found that as the average temperature increase rate in rapid temperature increase in primary recrystallization annealing increases, the number of Goss-oriented grains after primary recrystallization increases, and the iron loss value of the finally obtained grain-oriented electrical steel sheet decreases. If the average temperature increase rate in the rapid temperature increase in primary recrystallization annealing is increased, the degree of integration of crystal grains in the ideal Goss orientation after secondary recrystallization can be improved and the diameter of secondary recrystallized grains can be reduced, so the magnetic domain control process can be performed. Even if not performed, it is possible to reduce the iron loss value of the grain-oriented electrical steel sheet.

On the other hand, as a result of examination by the present inventors, it has been found that the shape of the steel sheet changes greatly depending on the conditions of rapid temperature increase in the temperature rising process of the primary recrystallization annealing. Specifically, it has been found that irregularities (wrinkles) are generated on the surface of the steel sheet depending on the magnitude of the tension applied in the sheet-threading direction of the steel sheet (hereinafter also referred to as steel sheet tension) during rapid temperature increase. In this case, when the grain-oriented electrical steel sheets are laminated in the production of the transformer, gaps are formed between the steel sheets, so the space factor of the iron core material decreases and the iron loss of the transformer increases.

The cause of the change in the shape of the steel sheet due to the rapid temperature increase in the primary recrystallization annealing is, for example, thermal expansion due to the rapid temperature increase, compared to the sheet width of the steel sheet on the low temperature side before the rapid temperature increase, on the high temperature side after the rapid temperature increase. It is conceivable that the sheet width of the steel sheet changes. In such a case, if the tension of the steel sheet is excessively increased, the high-temperature steel sheet, which has been elongated by thermal expansion, greatly contracts in the sheet width direction, resulting in a sharp difference in shape between the low-temperature steel sheet and the high-temperature side, resulting in wrinkles. It is thought to be Therefore, in the process of raising the temperature of the primary recrystallization annealing, in order to suppress the occurrence of wrinkles, it is important not to increase the tension of the steel sheet excessively.

Further, the present inventors have found that the upper limit of the steel sheet tension that does not cause wrinkles in the grain-oriented electrical steel sheet depends on the rapid temperature increase rate in the primary recrystallization annealing. Specifically, the present inventors have found that the upper limit of the steel sheet tension decreases as the temperature increase rate of rapid temperature increase increases. This is considered to be because, as the temperature increase rate of rapid temperature increase increases, the temperature difference between the steel sheet on the low temperature side before rapid temperature increase and the steel sheet on the high temperature side after rapid temperature increase increases, and shrinkage as a reaction to thermal expansion increases.

In addition, the present inventors, in the temperature raising process including rapid temperature raising in the temperature range of 550 ° C. to 700 ° C., the heating amount T (the difference between the temperature at the start of the heating process and the temperature at the end of the heating process) and the heating length L It has been found that the relationship of (the length of the steel sheet from the starting position of the heating process to the end position of the heating process) has a great influence on the shape of the steel sheet.

Specifically, the present inventors have found that a grain-oriented electrical steel sheet with fewer wrinkles can be obtained as the amount of heating T is smaller and the heating length L is longer. That is, the present inventors have found that a grain-oriented electrical steel sheet with a better shape can be obtained as T/L, which is a value obtained by dividing the heating amount T by the heating amount L, is smaller. This is because T/L represents the temperature change rate of the steel sheet in the sheet-threading direction, and as T/L increases, the temperature difference between the low-temperature side steel sheet and the high-temperature side steel sheet increases, and wrinkles are formed on the surface of the steel sheet due to the influence of thermal expansion. I guess it's because it's easier.

The present inventors came to conceive of this invention by considering the above knowledge. One embodiment of the present invention has the following structures.

It is a method for producing a grain-oriented electrical steel sheet, and the component composition is, in mass%,

C: 0.02% or more and 0.10% or less;

Si: 2.5% or more and 4.5% or less;

Mn: 0.01% or more and 0.15% or less;

Sum of S and Se: 0.001% or more and 0.050% or less;

Acid-soluble Al: 0.01% or more and 0.05% or less;

N: 0.002% or more and 0.015% or less

A step of obtaining a hot-rolled steel sheet by heating a slab containing Fe and impurities, the balance of which contains Fe and impurities, at 1280° C. to 1450° C., and performing hot rolling;

A step of obtaining a cold-rolled steel sheet by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing and then performing cold rolling twice or more with intermediate annealing interposed therebetween;

A step of subjecting the cold-rolled steel sheet to primary recrystallization annealing;

Applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, followed by final annealing to obtain a final annealed sheet;

A step of performing planarization annealing after applying an insulating film to the final annealing board

including,

In the temperature raising process of the primary recrystallization annealing, the average temperature increase rate V (℃/s) in the temperature range of 550 ℃ to 700 ℃ is 400 ℃ / s or more, including the temperature increase in the temperature range of 550 ℃ to 700 ℃ T/L (℃/mm), which is the ratio of the temperature increase amount T (℃) of a series of temperature increase processes to the heating length L (mm) of the series of temperature increase processes, is 0.1 ≤ T/L ≤ 4.0, and the cold-rolled steel sheet When the tension S (N/mm2) applied in the plate-threading direction is 1.96 ≤ S ≤ (19.6 - 1.96 × T / L) and V ≤ 1000, the tension S is 1.96 ≤ S ≤ (25.5 - 0.0137 × V) And, when V>1000, the tension S is 1.96≤S≤11.8.

In the grain-oriented electrical steel sheet manufactured by the above manufacturing method, the iron loss Wp in the case where the magnetic domain control treatment is not performed is 0.800 W/kg or less at W _17/50 . In the manufacturing method according to the present embodiment, the grain-oriented electrical steel sheet can be efficiently reduced in iron loss by rapidly increasing the temperature during the primary recrystallization annealing.

In addition, in the manufacturing method according to the present embodiment, the influence of thermal expansion of the steel sheet can be reduced by complexly and indivisibly controlling the steel sheet tension S, the average heating rate V, and T/L as described above. Therefore, the existence ratio of wrinkles having a steepness of 0.01 or more in the sheet width direction can be set to 0 wrinkles/m or more and 10 wrinkles/m or less.

Hereinafter, a method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment having the above-described characteristics will be described in more detail.

First, the component composition of the slab used in the method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment will be described. In addition, below, unless otherwise indicated, the notation "%" represents "mass %". A lower limit and an upper limit are included in the numerical limitation range described below. Numerical values expressed as "exceeding" or "less than" do not fall within the numerical range.

The content of C (carbon) is 0.02% or more and 0.10% or less. C has various roles, and when the content of C is less than 0.02%, the grain size becomes excessively large during heating of the slab, thereby increasing the iron loss value of the grain-oriented electrical steel sheet. When the content of C is more than 0.10%, the decarburization time becomes long during decarburization after cold rolling, and the manufacturing cost increases. Further, when the content of C is more than 0.10%, decarburization tends to be incomplete, and self-aging may occur in the grain-oriented electrical steel sheet. Therefore, the content of C is 0.02% or more and 0.10% or less. Preferably it is 0.05% or more or 0.09% or less.

The content of Si (silicon) is 2.5% or more and 4.5% or less. Si reduces iron loss by increasing the electrical resistance of the steel sheet, thereby reducing eddy current loss in the grain-oriented electrical steel sheet. When the Si content is less than 2.5%, it becomes difficult to sufficiently suppress eddy current loss in the grain-oriented electrical steel sheet. When the Si content exceeds 4.5%, the workability of the grain-oriented electrical steel sheet deteriorates. Therefore, the content of Si is 2.5% or more and 4.5% or less. Preferably it is 2.7% or more or 4.0% or less.

The content of Mn (manganese) is 0.01% or more and 0.15% or less. Mn forms MnS, MnSe, etc., which are inhibitors that influence secondary recrystallization. When the content of Mn is less than 0.01%, the absolute amounts of MnS and MnSe that cause secondary recrystallization are insufficient, so orientation control cannot be favorably performed. When the content of Mn is more than 0.15%, it is not preferable because solid solution of Mn becomes difficult at the time of heating the slab. Further, when the Mn content is more than 0.15%, the precipitated size of MnS and MnSe, which are inhibitors, tends to become coarse, and the optimal size distribution as an inhibitor is damaged, so that the inhibitor cannot be preferably controlled. Therefore, the content of Mn is 0.01% or more and 0.15% or less. Preferably it is 0.03% or more or 0.13% or less.

The total content of S (sulfur) and Se (selenium) is 0.001% or more and 0.050% or less. S and Se together with the aforementioned Mn form an inhibitor. Although both S and Se may be contained in the slab, at least one of them may be contained in the slab. When the total content of S and Se is out of the above range, a sufficient inhibitor effect cannot be obtained and orientation control cannot be performed favorably. Therefore, the content of S and Se is 0.001% or more and 0.050% or less in total. Preferably it is 0.005% or more or 0.040% or less.

The content of acid-soluble Al (acid-soluble aluminum) is 0.01% or more and 0.05% or less. Acid-soluble Al forms an inhibitor necessary for producing grain-oriented electrical steel sheets of high magnetic flux density. When the content of acid-soluble Al is less than 0.01%, the inhibitor strength is insufficient and orientation control cannot be favorably performed. When the content of acid-soluble Al is more than 0.05%, AlN precipitated as an inhibitor coarsens, the inhibitor strength decreases, and orientation control cannot be favorably performed. Therefore, the content of acid-soluble Al is 0.01% or more and 0.05% or less. Preferably it is 0.02% or more or 0.04% or less.

The content of N (nitrogen) is 0.002% or more and 0.015% or less. N together with the aforementioned acid-soluble Al forms AlN, an inhibitor. When the content of N is out of the above range, a sufficient inhibitor effect cannot be obtained and orientation control cannot be performed favorably. Therefore, the content of N is 0.002% or more and 0.015% or less. Preferably it is 0.005% or more or 0.012% or less.

The remainder of the slab used for manufacturing the grain-oriented electrical steel sheet according to the present embodiment is Fe and impurities. However, the slab used for manufacturing the grain-oriented electrical steel sheet according to the present embodiment contains any one of Cu, Sn, Ni, Cr, and Sb as an element that stabilizes secondary recrystallization in place of a part of Fe, which is the balance above, in addition to the above-mentioned elements. You may contain a species or 2 or more types. There is no need to limit the lower limit values of these selection elements, and the lower limit value may be 0%. Each content of these selection elements is good also as 0.01% or more and 0.30% or less. When the content of even one of these selected elements is 0.01% or more, the effect of stabilizing secondary recrystallization can be sufficiently obtained, and the core loss value of the grain-oriented electrical steel sheet can be further reduced. When the content of even one of these selected elements exceeds 0.30%, the effect of stabilizing secondary recrystallization is saturated and the manufacturing cost increases, which is not preferable.

A slab is formed by casting molten steel adjusted to the component composition described above. The casting method of the slab is not particularly limited. For example, a slab may be cast by a casting method such as a normal continuous casting method, an ingot method, and a thin slab casting method. In the case of continuous casting, the steel may be once cooled to a low temperature (for example, room temperature) and reheated, and then the steel may be hot-rolled, or the steel immediately after being cast (casting slab) may be continuously hot-rolled. Further, in research and development, even when steel ingots are formed in a vacuum melting furnace or the like, effects similar to those when slabs are formed have been confirmed with respect to the above component composition.

Subsequently, the inhibitor component in the slab is dissolved into solid solution by heating the slab to 1280°C or higher. When the heating temperature of the slab is less than 1280° C., it becomes difficult to sufficiently dissolve inhibitor components such as MnS, MnSe, and AlN, and thus orientation control cannot be favorably performed. The upper limit of the slab heating temperature at this time may be 1450°C or lower from the viewpoint of equipment protection.

A hot-rolled steel sheet is obtained by subjecting the heated slab to hot rolling. The sheet thickness of the hot-rolled steel sheet may be, for example, 1.8 mm or more and 3.5 mm or less. When the sheet thickness of the hot-rolled steel sheet is less than 1.8 mm, the temperature of the steel sheet after hot rolling becomes low and the amount of AlN precipitated in the steel sheet increases, resulting in destabilization of secondary recrystallization, resulting in magnetic properties in a grain-oriented electrical steel sheet having a finally obtained sheet thickness of 0.23 mm or less. There may be times when this decreases. When the plate|board thickness of a hot-rolled steel plate exceeds 3.5 mm, the rolling load in a cold rolling process may become large.

After hot-rolled steel sheet is subjected to hot-rolled sheet annealing, a cold-rolled steel sheet is obtained by performing one cold rolling or multiple times of cold rolling with intermediate annealing interposed therebetween. When a hot-rolled steel sheet is rolled by multiple rounds of cold rolling with intermediate annealing interposed therebetween, it is also possible to omit the hot-rolled sheet annealing in the previous stage. However, since the shape of the steel sheet can be made better by performing the hot-rolled sheet annealing, the possibility of the steel sheet breaking during cold rolling can be reduced. Therefore, even when cold rolling is performed on a hot-rolled steel sheet a plurality of times with intermediate annealing interposed therebetween, it is preferable to perform hot-rolled sheet annealing at the front end. The conditions of the hot-rolled sheet annealing are not particularly limited, but may be general conditions. For the hot-rolled steel sheet after hot rolling, in the case of continuous annealing, soaking at 750 to 1200 ° C. for 10 seconds to 10 minutes, and in the case of batch annealing, 650 to 950 What is necessary is just to perform cracking for 30 minutes to 24 hours at °C.

The steel sheet may be heat treated at about 300°C or less between passes of cold rolling, between rolling roll stands, or during rolling. By performing the heat treatment, the magnetic properties of the finally obtained grain-oriented electrical steel sheet can be further improved. Also, although the hot-rolled steel sheet may be rolled by cold rolling three or more times, it is preferable that the hot-rolled steel sheet is rolled by cold rolling once or twice because multiple cold rolling increases manufacturing cost.

After the cold-rolled steel sheet is rapidly heated, decarburization annealing is performed. These processes (rapid temperature rising and decarburization annealing) are also referred to as primary recrystallization annealing, and are preferably performed continuously. In a cold-rolled steel sheet by primary recrystallization annealing, it is possible to reduce the diameter of secondary recrystallized grains after secondary recrystallization while increasing the Goss orientation grains before secondary recrystallization.

In the manufacturing method according to the present embodiment, in the heating process in the primary recrystallization annealing, the average heating rate V in the temperature range of 550 °C to 700 °C is set to 400 °C/s or more. By performing the rapid temperature increase as described above in the temperature rising process in the primary recrystallization annealing, the diameter of the secondary recrystallized grains after the secondary recrystallization can be reduced while further increasing the Goss orientation grains before the secondary recrystallization of the cold-rolled steel sheet.

When the average temperature increase rate V in the temperature range of 550 ° C to 700 ° C is 700 ° C / s or more, since the number of Goss-oriented grains before secondary recrystallization can be further increased, the core loss of the finally obtained grain-oriented electrical steel sheet can be further reduced. can On the other hand, when the average temperature increase rate V is less than 400 ° C. / s, since the crystal grains after secondary recrystallization are reduced, it becomes difficult to form sufficient Goss-oriented grains, and the iron loss of the finally obtained grain-oriented electrical steel sheet increases. The upper limit of the average temperature increase rate V is not particularly limited, but may be, for example, 3000°C/s from the viewpoint of equipment and manufacturing cost.

Here, a heat pattern in the temperature rising process of primary recrystallization annealing will be described with reference to FIGS. 1 to 4 . 1 to 4 are views showing specific examples of heat patterns in the temperature rising process of primary recrystallization annealing.

As shown in FIG. 1 , only one heating device 10 for heating the steel sheet 1 from 550°C to 700°C may be used. In this case, the average temperature increase rate V is the temperature increase starting point (temperature increase start point A) in the temperature increase process (temperature increase device 10) including the temperature increase from 550 ° C. to 700 ° C. It is taken as the average value of the temperature increase rate up to the end point B).

As shown in FIG. 2 , a plurality of temperature increasing devices 21 and 22 may be used to heat the steel sheet 1 from 550°C to 700°C. In this case, the average temperature increase rate V is the temperature increase process including 550 ° C. From the point at which the temperature is raised (temperature rising starting point A), in the temperature increasing device 22, the temperature raising process including 700°C (including the temperature rise from a temperature range of less than 700°C to a temperature range of more than 700°C) The average value of the temperature increase rate up to the temperature increase end point (temperature increase end point B) in .

That is, the temperature increase start point A is the point at which the temperature of the steel sheet 1 transitions from a state in which the temperature of the steel sheet 1 decreases to a state in which the temperature of the steel sheet 1 rises on the low temperature side of the temperature rise process including 550 ° C. is the point that takes the minimum value in the graph of the pattern). In addition, the temperature increase end point B is the point at which the temperature of the steel plate 1 transitions from a state in which the temperature of the steel plate 1 rises to a state in which the temperature of the steel plate 1 decreases (that is, a graph of a heat pattern) on the high temperature side of the temperature rise process including 700 ° C. is the point taking the maximum value at ).

However, as shown in Fig. 3, when the temperature of the steel sheet 1 continues to rise even on the lower temperature side than the temperature raising process including 550 ° C. The starting point A may be a point (point A in FIG. 3 ) at which the rate of change in the rate of temperature increase reaches a maximum positive value at 550°C or lower. In addition, as shown in FIG. 4, when the temperature of the steel sheet 1 continues to rise even on the higher temperature side than the temperature raising process including 700 ° C. by the arrangement of the plurality of heating devices 41 and 42, the temperature increase end point B is , 700° C. or higher, the rate of change of the temperature increase rate is a negative value and is minimum (point B in FIG. 4).

That is, the temperature increase start point A and the temperature increase end point B may not coincide with the inlet and outlet of the temperature increase device depending on the heater configuration, heating capability and arrangement of the temperature increase device.

In the temperature raising process of the primary recrystallization annealing, the heat pattern in the temperature range of 550° C. to 700° C. is not particularly limited, and the heat pattern between the temperature raising devices when there are a plurality of temperature raising devices is not particularly limited. The temperature raising method or temperature raising device in the temperature raising process is not particularly limited either, but, for example, an energization heating method or an induction heating method may be used. In the temperature raising process of the primary recrystallization annealing, the heat pattern in the temperature range other than the temperature range of 550 ° C to 700 ° C is not particularly limited, but before the temperature raising process including the temperature range of 550 ° C to 700 ° C, the temperature of the steel sheet is 550 ° C. C or more is undesirable because the effect of rapid temperature increase in primary recrystallization annealing is reduced.

Here, the method for determining the temperature increase start point A and the temperature increase end point B is not particularly limited, but can be determined by measuring the temperature of the steel sheet outside the temperature increase device and inside the temperature increase device using, for example, a radiation thermometer or the like. In addition, it does not specifically limit about the measuring method of steel plate temperature.

If it is difficult to measure the temperature of the steel sheet and it is difficult to determine the temperature increase start point A and the temperature increase end point B, the heat patterns of the heating process and cooling process are inferred based on the sheet thickness of the steel sheet to be passed through, so that the temperature increase start point A and The temperature increase end point B may be estimated. Furthermore, it is good also considering the temperature increase device inlet side temperature and temperature increase device outlet side temperature of a steel plate in a temperature increase process as temperature increase start point A and temperature increase end point B.

In the present embodiment, T/L (°C/mm), which is the ratio of the temperature increase amount T (°C) and the heating length L (mm) in the temperature raising process including rapid temperature increase in the temperature range of 550°C to 700°C, is 0.1≤T/ It is controlled by L≤4.0. Here, the temperature increase amount T represents the amount of temperature increase from the temperature increase start point A to the temperature increase end point B, and the heating length L refers to the length of the steel sheet passing through the temperature increase device from the temperature increase start point A to the temperature increase end point B described above. indicate Therefore, when there are a plurality of heating devices, the heating length L also includes the length between the heating devices.

T/L, which is the ratio between the amount of temperature increase T and the heating length L, represents the temperature change rate in the longitudinal direction of the steel sheet in primary recrystallization annealing. Therefore, the larger the T/L, the larger the difference in sheet thickness due to thermal expansion between the steel sheet on the low temperature side and the steel sheet on the high temperature side. When T/L is large, the shrinkage of the sheet width in the high-temperature steel sheet becomes larger than that in the low-temperature side steel sheet, so it is considered that wrinkles easily occur on the surface of the steel sheet. Therefore, it is thought that the larger the T/L, the more wrinkles on the surface of the grain-oriented electrical steel sheet change due to the change in shape of the grain-oriented electrical steel sheet.

The upper limit of T/L at which the ratio of wrinkles present on the surface of a grain-oriented electrical steel sheet can be suppressed is 4.0°C/mm, as can be seen from examples described later. Preferably T/L is 2.7°C/mm or less.

Since T/L becomes smaller as the heating amount T is smaller and the heating length L is longer, it becomes possible to obtain a grain-oriented electrical steel sheet with fewer wrinkles and a good surface shape. However, T/L has a lower limit in terms of equipment constraints. This is because it is important to rapidly raise the temperature from at least 550°C to 700°C in order to improve the magnetic properties of the grain-oriented electrical steel sheet by rapid temperature increase in primary recrystallization annealing, and there is a limit to reducing the amount of temperature increase T. am. In addition, the longer the heating length L, the larger the installation space of the heating device becomes, and it becomes difficult to increase the speed of sheet passing of the steel sheet. Therefore, the lower limit of T/L is 0.1°C/mm from the point of view of equipment constraints. Preferably T/L is 0.2°C/mm or more.

The shape of the grain-oriented electrical steel sheet also changes depending on the magnitude of the tension S (N/mm2) (ie, the steel sheet tension S (N/mm2)) applied in the sheet-threading direction of the steel sheet in the heating process of the primary recrystallization annealing. . This is considered to be because, when the steel sheet tension S is excessively large, the steel sheet thermally expanded during the rapid temperature increase in primary recrystallization annealing tends to shrink in the width direction, and wrinkles are formed on the surface of the grain oriented electrical steel sheet. Therefore, the upper limit of the steel sheet tension S, which does not cause wrinkles in the grain-oriented electrical steel sheet, depends on the average temperature increase rate V (°C/s) in rapid temperature increase. In addition, the magnitude of the effect of increasing the Goss-oriented grains due to the rapid temperature increase also varies according to the magnitude of the steel sheet tension S applied to the steel sheet during the rapid temperature increase of the primary recrystallization annealing. Therefore, the magnitude of the steel sheet tension S during rapid temperature increase in primary recrystallization annealing is affected by the average temperature increase rate V (°C/s) during rapid temperature increase.

Specifically, with respect to the average heating rate V (°C/s) in the heating process, the steel sheet tension S (N/mm2) is 1.96 ≤ S ≤ (19.6 - 1.96 × T/L), and the steel sheet tension S is V ≤ In the case of 1000, 1.96≤S≤(25.5-0.0137 × V), and in the case of V>1000, 1.96≤S≤11.8. In addition, the steel sheet tension S is an average value of the steel sheet tension in a temperature rising process including rapid temperature rising in the temperature range of 550°C to 700°C.

When the steel sheet tension S exceeds the upper limit value depending on the average heating rate V, the shape of the finally obtained grain-oriented electrical steel sheet deteriorates due to the tension applied in the sheet-threading direction, and surface wrinkles increase. In addition, due to the tension applied in the sheet-threading direction of the steel sheet, the aggregate structure of the crystal grains generated in the primary recrystallization is disturbed, and orientation control cannot be preferably performed. On the other hand, when the steel sheet tension S is less than 1.96 N/mm 2 , the steel sheet meandering during sheet passing may cause breakage of the steel sheet and equipment damage.

The rapidly heated steel sheet is subjected to decarburization annealing at a temperature of 900° C. or less for 30 seconds to 10 minutes in a humid atmosphere containing hydrogen and nitrogen. Further, in primary recrystallization annealing consisting of rapid temperature rise and decarburization annealing, reduction annealing may be performed subsequent to decarburization annealing for the purpose of improving the magnetic properties and film properties of the cold-rolled steel sheet. In addition, although the rapid heating process and the decarburization annealing process may be different processes, they may be performed continuously from the viewpoint of omitting the manufacturing process line. When performing the rapid temperature increase and the decarburization annealing continuously, the rapid temperature increase step and the decarburization annealing step may be connected by a throat or the like.

After applying an annealing separator containing MgO as a main component to the cold-rolled steel sheet after primary recrystallization annealing, final annealing is performed to obtain a final annealed sheet. Secondary recrystallization occurs in finish annealing. Further, a forsterite film is formed on the surface of the silicon steel sheet (cold rolled steel sheet) by performing finish annealing after the annealing separator is applied.

Finish annealing may be performed by holding the coiled cold-rolled steel sheet to which the annealing separator is applied at a temperature of 800°C to 1000°C for 20 hours or longer using, for example, a batch heating furnace or the like. Further, in order to further reduce the iron loss value of the finally obtained grain-oriented electrical steel sheet, a purification treatment may be performed in which the temperature of the coiled finish annealed sheet is raised to a temperature of about 1200°C and then maintained.

There is no particular limitation on the average temperature increase rate in the temperature increase process of the finish annealing, and any general conditions of the finish annealing may be used. For example, the average temperature increase rate in the temperature increase process of the final annealing may be 5°C/h to 100°C/h from the viewpoint of productivity and general equipment constraints. In addition, the heating process of the final annealing may be performed by another known heat pattern. The atmospheric gas composition in the final annealing is not particularly limited. In the secondary recrystallization process, a mixed gas of nitrogen and hydrogen may be used. A dry atmosphere may be sufficient, and even if it is a wet atmosphere, it does not matter. The atmosphere gas composition of the purification process may be dry hydrogen gas.

After finish annealing, for the purpose of imparting insulating properties and tension to the finish annealing board, an insulating film containing, for example, aluminum phosphate and colloidal silica as main components is applied to the surface of the finish annealing board. Thereafter, flattening annealing is performed for the purpose of flattening the steel sheet shape deformed by baking of the insulating film and final annealing. Flattening annealing may be performed under known conditions, and may be performed, for example, by holding the final annealed sheet in a temperature range of 800°C to 950°C for 10 seconds or longer. In addition, the component of the insulating film is not particularly limited as long as it imparts insulating properties and tension to the final annealed board.

The grain-oriented electrical steel sheet according to the present embodiment can be manufactured by the manufacturing method described above. A grain-oriented electrical steel sheet according to the present embodiment manufactured by such a manufacturing method is as follows.

a silicon steel sheet;

A forsterite film disposed on the silicon steel sheet;

A grain-oriented electrical steel sheet having an insulating film disposed on the forsterite film,

The silicon steel sheet has a component composition in mass%,

Si: 2.5% or more and 4.5% or less;

Mn: 0.01% or more and 0.15% or less;

Sum of S and Se: 0% or more and 0.005% or less;

Acid soluble Al: 0% or more and 0.01% or less, and

N: 0% or more and 0.005% or less

and the balance includes Fe and impurities,

The average particle diameter of the secondary recrystallized grains of the silicon steel sheet is 10 mm or more and 50 mm or less,

The grain-oriented electrical steel sheet,

The plate thickness is 0.15 mm or more and 0.23 mm or less,

Iron loss Wp is 0.800 W/kg or less with W _17/50 ,

The presence ratio of wrinkles having a steepness degree of 0.01 or more is 0 / m or more and 10 / m or less in the sheet width direction,

The magnetic flux density B8 value is 1.930T or more.

In the grain-oriented electrical steel sheet according to the present embodiment, it is important to control the contents of Si and Mn in the component composition contained in the silicon steel sheet of the grain-oriented electrical steel sheet in order to achieve low core loss even without magnetic domain control treatment.

Si reduces eddy current loss constituting a part of iron loss by increasing the electrical resistance of the steel sheet. Si is preferably contained in the silicon steel sheet in the range of 2.5% or more and 4.5% or less in terms of mass%. Preferably it is 2.7% or more or 4.0% or less. When the content of Si is less than 2.5%, it becomes difficult to suppress eddy current loss in the grain-oriented electrical steel sheet. When the Si content exceeds 4.5%, the workability of the grain-oriented electrical steel sheet deteriorates.

Mn forms MnS and MnSe, which are inhibitors that influence secondary recrystallization. Mn is preferably contained in the silicon steel sheet in a range of 0.01% or more and 0.15% or less in terms of mass%. Preferably it is 0.03% or more or 0.13% or less. When the content of Mn is less than 0.01%, the absolute amounts of MnS and MnSe that cause secondary recrystallization are insufficient, so orientation control cannot be favorably performed. When the content of Mn is more than 0.15%, it becomes difficult to dissolve Mn during heating of the slab, and the optimum size distribution of the inhibitor is damaged due to the coarsening of the precipitate size of the inhibitor, so that the inhibitor cannot be controlled favorably. .

The remainder of the silicon steel sheet according to the present embodiment is Fe and impurities. However, C, S, Se, acid-soluble Al and N, and any one or two or more of Cu, Sn, Ni, Cr, and Sb as elements stabilizing the secondary recrystallization are contained instead of part of Fe as the remainder. You can do it. There is no need to limit the lower limit values of these selection elements, and the lower limit value may be 0%.

Although the C content is preferably lower, it is good also as 0.0050% or less. If the C content exceeds 0.0050% even after decarburization annealing, magnetic aging may occur and the magnetic properties of the grain-oriented electrical steel sheet may deteriorate.

Although the content of S and Se is preferably lower, it is good also as 0.005% or less in total. When the total content of S and Se exceeds 0.005%, magnetic aging may occur and the magnetic properties may deteriorate.

The N content is preferably lower, but it may be 0.010% or less. When the N content is more than 0.010%, magnetic aging may occur and the magnetic properties may deteriorate. More preferably, it is good also as 0.005% or less.

The acid-soluble Al content is preferably lower, but may be 0.01% or less. When the acid-soluble Al content is more than 0.01%, magnetic aging may occur and the magnetic properties may deteriorate.

Each content of Cu, Sn, Ni, Cr, and Sb may be 0.01% or more and 0.30% or less. When the content of at least one of these elements is 0.01% or more, the effect of stabilizing secondary recrystallization is sufficiently obtained, the iron loss value can be further reduced, and better magnetic properties can be obtained. If the content of any one of these elements exceeds 0.30%, the effect of stabilizing secondary recrystallization is saturated, which is not preferable from the viewpoint of suppressing an increase in the manufacturing cost of the grain-oriented electrical steel sheet.

The component composition of the silicon steel sheet may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) for the obtained silicon steel sheet after removing the insulating coating and the forsterite coating of the grain-oriented electrical steel sheet. In addition, C and S may be measured using a combustion-infrared absorption method, and N may be measured using an inert gas melting-thermal conductivity method.

In addition, the method for removing the insulating film and the forsterite film of the grain-oriented electrical steel sheet is specifically as follows. A silicon steel sheet is obtained by removing the insulating film and the forsterite film of the grain-oriented electrical steel sheet. Specifically, the grain-oriented electrical steel sheet is immersed in an aqueous sodium hydroxide solution of NaOH: 20% by mass + H ₂ O: 80% by mass at 80°C for 20 minutes, then washed with water and dried to remove the insulating film from the grain-oriented electrical steel sheet. Then, the grain-oriented electrical steel sheet was immersed in an aqueous solution of HCl: 20% by mass + H ₂ O: 80% by mass at 50 ° C. for 2 minutes, then washed with water and dried to remove the forsterite film of the grain-oriented electrical steel sheet, and silicon get a grater In addition, the immersion time in the sodium hydroxide aqueous solution or hydrochloric acid aqueous solution may be changed according to the thickness of the film.

In the silicon steel sheet according to the present embodiment, the average grain size of secondary recrystallized grains is controlled. In the silicon steel sheet according to the present embodiment, the average particle diameter of the secondary recrystallized grains is 10 mm or more and 50 mm or less. Preferably it is 40 mm or less.

When the average particle diameter of the secondary recrystallized grains exceeds 50 mm, the iron loss value (especially eddy current loss) of the grain-oriented electrical steel sheet becomes large. The lower limit of the average grain size of the secondary recrystallized grains may be, for example, 10 mm in order to satisfy the magnetic properties of the grain-oriented electrical steel sheet according to the present embodiment.

The average particle diameter of the secondary recrystallized grains of the silicon steel sheet can be measured, for example, by the following method.

The insulating film and the forsterite film of the grain-oriented electrical steel sheet are removed by the same method as the above-mentioned method. In the obtained silicon steel sheet, pits along the crystal orientation are formed on the surface of the steel sheet during immersion in an aqueous hydrochloric acid solution, so that the steel structure of the silicon steel sheet can be observed. A test piece is cut out so that the observation surface is at least 60 mm wide x 300 mm long, the steel structure of the silicon steel sheet is observed, and grain boundaries that can be recognized macroscopically are traced with an oil pen. At least five surface images of the grain-oriented electrical steel sheet are acquired using a commercially available image scanner device, and the acquired images are analyzed using commercially available image analysis software. The average grain size of secondary recrystallized grains of the grain oriented electrical steel sheet is obtained by measuring the equivalent circle diameter of the crystal grains of the grain oriented electrical steel sheet in all images by image analysis and then calculating the average value of the measured equivalent circle diameters.

In addition, for example, small crystal grains having a particle size of less than 2 mm, which is difficult to visually identify, are excluded from the particle size measurement of secondary recrystallized grains.

The forsterite film disposed on the silicon steel sheet mainly contains Mg ₂ SiO ₄ , and contains trace amounts of impurities and additives contained in the silicon steel sheet or the annealing separator and reaction products thereof.

The insulating film disposed on the forsterite film is mainly composed of phosphate and colloidal silica, and contains trace amounts of elements and impurities diffused from the silicon steel sheet during purification annealing and reaction products thereof. In addition, components other than the above may be used as long as insulation properties and tensile strength with respect to the steel sheet are obtained.

The sheet thickness of the grain-oriented electrical steel sheet according to the present embodiment is 0.15 mm or more and 0.23 mm or less. When the thickness of the grain-oriented electrical steel sheet is less than 0.15 mm, the load of cold rolling significantly increases. When the thickness of the grain-oriented electrical steel sheet exceeds 0.23 mm, the core loss of the grain-oriented electrical steel sheet deteriorates.

The sheet thickness of the grain-oriented electrical steel sheet may be determined by measuring with radiation or the like. It is also possible to simply take a sample of a predetermined size from the grain-oriented electrical steel sheet by shearing, and calculate it by converting it from the weight of the steel sheet using the density of iron. Alternatively, it may be obtained by converting from the coil diameter and the number of turns of the steel sheet. Moreover, it is preferable that the density of iron is selected according to the amount of Si contained.

The value of magnetic flux density B8 of the grain-oriented electrical steel sheet is 1.930T or more. Here, the magnetic flux density B8 value is an average value of magnetic flux densities when a magnetic field of 800 A/m is applied.

When the magnetic flux density B8 value is less than 1.930T, the core loss value (especially hysteresis loss) of the grain-oriented electrical steel sheet becomes large. Although the upper limit of the magnetic flux density B8 value is not particularly limited, realistically, it may be, for example, 2.000T. In addition, the magnetic properties of the grain oriented electrical steel sheet, such as magnetic flux density, can be measured by known methods. For example, the magnetic properties of a grain-oriented electrical steel sheet are measured using a method based on the Epstein test specified in JIS C 2550:2011 or a single sheet tester (SST) specified in JIS C 2556:2015. It can be measured by doing, but in this embodiment, it is obtained by a method based on the Epstein test specified in JIS C 2550:2011. In the measurement of the magnetic flux density B8 value, one set of samples is taken from both ends in the longitudinal direction of the coil of the grain-oriented electrical steel sheet after the final step, and the average value of the magnetic flux density B8 values obtained using those samples is obtained. Alternatively, after the coil is divided in the longitudinal direction, samples may be taken one set at a time from both ends in the longitudinal direction of the divided coil. In addition, in the case where a sufficient length is not obtained in the longitudinal direction of the coil at the time of sampling, and only one sample can be taken, it is okay to use the measured value of one sample.

In the grain-oriented electrical steel sheet according to the present embodiment, the existence ratio of wrinkles having a steepness of 0.01 or more is 0 wrinkles/m or more and 10 wrinkles/m or less in the sheet width direction. Since the grain-oriented electrical steel sheet manufactured by the manufacturing method according to the present embodiment has a good surface shape, when the grain-oriented electrical steel sheet is laminated, the existence ratio of wrinkles with a steepness degree of 0.01 or more, which lowers the space factor of the iron core material, can be reduced. .

A method for obtaining the degree of steepness will be described with reference to FIG. 5 . Fig. 5 is a diagram showing a cross-sectional curve (bending curve) of a grain-oriented electrical steel sheet obtained by measuring the surface of the grain-oriented electrical steel sheet with a laser displacement meter.

The steepness is calculated by measuring the shape of the convex portion present on the surface of the grain-oriented electrical steel sheet. First, the shape of the steel sheet in the sheet width direction is measured with a laser displacement meter to obtain a cross-sectional curve of the grain oriented electrical steel sheet in the sheet width direction shown in FIG. 5 . When the noise of the cross-sectional curve is large, the noise may be removed within a range that does not greatly deviate from the measured cross-sectional curve. A convex part having a peak height h of 0.1 mm or more is extracted from this cross-sectional curve. The peak height h extracted as a convex portion is more preferably 0.05 mm or more. The peak height h is the distance between the straight line connecting the two lowest points (points a and b in FIG. 5 ) near the convex portion and the highest point (point c in FIG. 5 ) of the convex portion. The steepness of the extracted convexity is obtained by dividing the peak height h of the extracted convexity by 1/2 of the length L of the straight line connecting the two lowest points (points a and b in Fig. 5) near the extracted convexity (i.e., Steepness=2h/L). In the present embodiment, convex portions having a steepness degree of 0.01 or more obtained by the above method are regarded as wrinkles, and the number of wrinkles having a steepness degree of 0.01 or more existing per 1 m in the sheet width direction of the grain-oriented electrical steel sheet is obtained. Furthermore, cross-sectional curves are obtained from at least four or more locations of the grain-oriented electrical steel sheet so that the total length is 4 m in the sheet width direction, and the number of wrinkles is obtained by the above method.

In the grain-oriented electrical steel sheet according to the present embodiment, as described above, it is possible to reduce the iron loss value even without performing magnetic domain control. Specifically, in the grain-oriented electrical steel sheet according to the present embodiment, the iron loss Wp in the case where the magnetic domain control treatment is not performed is 0.800 W/kg or less in terms of W _17/50 . Preferably it is 0.790 W/kg or less, More preferably, it is 0.785 W/kg or less. Although there is no need to specifically limit the lower limit, it is good also as 0.600 W/kg from the viewpoint of industrially stable manufacturability. Here, the iron loss Wp in the case where the magnetic domain control treatment is not performed uses a value measured on a grain-oriented electrical steel sheet after stress relief annealing. W _17/50 is an average value of iron loss when a grain-oriented electrical steel sheet is excited at 1.7 T at 50 Hz. In the measurement of iron loss Wp, samples are taken one set each from both ends in the longitudinal direction of the coil of the grain-oriented electrical steel sheet after the final process, and the average value of iron loss obtained using these samples is obtained. Alternatively, after the coil is divided in the longitudinal direction, samples may be taken one set at a time from both ends in the longitudinal direction of the divided coil. In addition, in the case where a sufficient length is not obtained in the longitudinal direction of the coil at the time of sampling, and only one sample can be taken, it is okay to use the measured value of one sample.

As described above, in the grain-oriented electrical steel sheet according to the present embodiment, core loss can be sufficiently reduced even without magnetic domain control processing. Although the magnetic domain control process can reduce the iron loss value of the grain-oriented electrical steel sheet, it increases the noise of a transformer using the grain-oriented electrical steel sheet as an iron core material. Therefore, the grain-oriented electrical steel sheet according to the present embodiment can achieve both magnetic characteristics and noise characteristics of a transformer.

According to the method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment, it is possible to manufacture a grain-oriented electrical steel sheet with sufficiently reduced iron loss and a good surface shape even without magnetic domain control treatment. Since the grain-oriented electrical steel sheet according to the present embodiment manufactured by the manufacturing method has a good surface shape, the space factor can be improved when used as an iron core material for a transformer. In this embodiment, it goes without saying that the magnetic domain control treatment may be applied to the grain-oriented electrical steel sheet depending on the purpose of the customer.

Example

Below, the grain-oriented electrical steel sheet manufacturing method and the grain-oriented electrical steel sheet according to the present embodiment will be described in more detail while showing examples. In addition, the examples shown below are merely examples of the grain-oriented electrical steel sheet according to the present embodiment, and the grain-oriented electrical steel sheet according to the present embodiment is not limited to the examples shown below.

(Example 1)

In terms of mass%, a slab containing C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, N: 0.008%, the remainder containing Fe and impurities, was fabricated. did After heating the slab at 1350°C for 1 hour, hot rolling was performed to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. The obtained hot-rolled steel sheet was subjected to hot-rolled sheet annealing at a maximum temperature of 1100°C for 140 seconds, pickling, and then cold rolling to obtain a cold-rolled steel sheet having a thickness of 0.23 mm.

Subsequently, the obtained cold-rolled steel sheet was rapidly heated at an average temperature increase rate V (°C/s) shown in Tables 1 and 2 while adding a steel sheet tension S (N/mm 2 ) shown in Tables 1 and 2. At this time, the average temperature increase rate V (°C/s) is the average value of the temperature increase rates in the temperature range of 550°C to 700°C, and the temperature increase output of the temperature increase device and the distance between the devices are changed, and the temperature increase device is replaced. By doing so, the temperature increase amount T (°C) and heating length L (mm) were changed as shown in Tables 1 and 2. Here, the temperature increase starting point A is the temperature at the inlet side of the temperature increasing device in the temperature increasing process including 550°C, and the temperature increasing end point B is the temperature at the exit side of the temperature increasing device during the temperature increasing process including 700°C. The average from A to the temperature increase end point B was taken as the average temperature increase rate V (°C/s). Thereafter, decarburization annealing was performed in a hydrogen atmosphere at 850° C. for 180 seconds.

Next, after applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, finish annealing was performed to obtain finish annealing, and the finish annealing sheet was washed with water. Thereafter, an insulating film containing aluminum phosphate and colloidal silica as main components is applied to the surface of the final annealing plate, and then baking of the insulating film and flattening annealing for the purpose of flattening the steel sheet are performed so that the sheet thickness is 0.15 mm or more. A grain-oriented electrical steel sheet of 0.23 mm or less was obtained.

Samples of the Epstein method are taken one by one by shearing from both ends of the coil of the grain-oriented electrical steel sheet obtained by the above method in the sheet width direction, and after performing stress relief annealing on these samples, according to the Epstein method specified in JIS C2550: 2011 Based on this, iron loss Wp and magnetic flux density B8 values were measured. The iron loss Wp was measured by W _17/50 and was the average value of the iron loss obtained by excitation at 50 Hz and 1.7 T. The magnetic flux density B8 value was an average value of magnetic flux densities obtained by applying a magnetic field of 800 A/m at 50 Hz.

In addition, two samples were each taken by shearing from both ends of the coil of the grain-oriented electrical steel sheet in the sheet width direction, and the surface shape in the sheet width direction was measured with a laser displacement meter to obtain a cross-sectional curve. Using the obtained cross-sectional curve, the number of wrinkles having a steepness of 0.01 or more existing per 1 m in the sheet width direction of the grain-oriented electrical steel sheet was obtained by the method described above.

In addition, after the insulation film and forsterite film of the grain-oriented electrical steel sheet obtained were removed by the above-described method, the component composition of the silicon steel sheet was measured using ICP-AES. In addition, the average particle diameter of the secondary recrystallized grains of the silicon steel sheet was measured by the method described above.

When the core loss Wp was 0.800 or less and the wrinkle ratio was 0/m or more and 10/m or less, it was judged as pass. When any of these conditions were not satisfied, it was determined as disqualified and described as "C" in the evaluation column in the table. The iron loss Wp of the examples judged as acceptable was evaluated based on the following criteria.

S (extremely good): 0.785 W/kg or less

A (better): Wp greater than 0.785 W/kg and 0.790 W/kg or less

B (Good): Wp is more than 0.790W/kg and 0.800W/kg or less

Table 1 and Table 2 show the manufacturing conditions, measurement results, and evaluation results of grain-oriented electrical steel sheets. Further, in the example of the present invention, in the component composition of the silicon steel sheet, the total content of S and Se is 0.005% or less, the acid-soluble Al content is 0.01% or less, the N content is 0.005% or less, and the balance is Fe and impurities. was

Referring to the results of Tables 1 and 2, it was found that the grain-oriented electrical steel sheets (examples of the present invention) satisfying the conditions of the present embodiment had an evaluation of B or higher (good or higher). In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C to 700 ° C in the primary recrystallization annealing was 700 ° C / s or more, the iron loss Wp was 0.790 W / kg or less, and the evaluation was A or more ( It was found to be better than better). In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 1000 ° C./s or more, the iron loss Wp was 0.785 W / kg or less, and the evaluation was S (extremely good). It was found that

FIG. 6 shows a graph plotting the results shown in Tables 1 and 2, with the temperature increase rate V taken on the abscissa and the steel sheet tension S taken on the ordinate. 7 shows a graph in which the results shown in Tables 1 and 2 are plotted with T/L taken on the abscissa axis and steel sheet tension S taken on the ordinate axis. 6 and 7, the examples of the present invention are plotted with ○ marks, and the comparative examples are plotted with × marks.

As shown in Fig. 6, between the heating rate V (°C/s) and the steel sheet tension S (N/mm2) in the heating process of the primary recrystallization annealing, as defined in the manufacturing method according to the present embodiment, the following It can be seen that it is necessary to satisfy the relationships of Equations 1 and 2 of Therefore, according to the manufacturing method according to the present embodiment, it is possible to manufacture a grain-oriented electrical steel sheet having a reduced core loss value.

1.96≤S≤(25.5-0.0137×V)(V≤1000)... Equation 1

1.96≤S≤11.8 (V>1000)... Equation 2

In addition, as shown in FIG. 7, as defined in the manufacturing method according to the present embodiment, the steel sheet tension S (N / mm ) and T / L (° C. / mm) in the heating process of the primary recrystallization annealing are It can be seen that the number of wrinkles in the grain-oriented electrical steel sheet can be reduced by specifying as in Equations 3 and 4.

0.1≤T/L≤4.0... Equation 3

1.96≤S≤(19.6-1.96×T/L)... Equation 4

(Example 2)

In terms of mass%, C: 0.08%, S: 0.023%, acid-soluble Al: 0.03%, N: 0.008%, the balance being Si and Mn, Fe and impurities in the amounts shown in Tables 3 and 4. A slab containing After heating the slab at 1350°C for 1 hour, hot rolling was performed to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. A cold-rolled steel sheet having a thickness of 0.23 mm was obtained by subjecting the obtained hot-rolled steel sheet to hot-rolled sheet annealing at a maximum temperature of 1100°C for 140 seconds, pickling, and then cold rolling.

Subsequently, the obtained cold-rolled steel sheet was rapidly heated at a heating rate V (° C./s) shown in Tables 3 and 4 below, and then subjected to decarburization annealing in a hydrogen atmosphere at 850° C. for 180 seconds. In addition, the average temperature increase rate V (°C / s) is the average value of the temperature increase rate in the temperature range of 550 ° C to 700 ° C, and in the temperature increase process of the primary recrystallization annealing, in the plate-threading direction of the cold-rolled steel sheet, 7.84 N / mm The steel sheet tension S was applied. In addition, the temperature increase amount T was 400 degreeC and the heating length L was 400 mm. The average temperature increase rate V was calculated by the same method as in Example 1.

After applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, finish annealing was performed to obtain finish annealing, and the finish annealing sheet was washed with water. Thereafter, an insulating film containing aluminum phosphate and colloidal silica as main components is applied to the surface of the final annealing plate, and then baking of the insulating film and flattening annealing for the purpose of flattening the steel sheet are performed so that the sheet thickness is 0.15 mm or more. A grain-oriented electrical steel sheet of 0.23 mm or less was obtained.

Regarding the grain-oriented electrical steel sheet obtained by the above method, the iron loss Wp, the magnetic flux density B8 value, the number of wrinkles having a steepness of 0.01 or more per 1 m in the sheet width direction, the component composition of the silicon steel sheet, and The average particle diameter of secondary recrystallized grains was measured.

When the core loss Wp was 0.800 or less and the wrinkle ratio was 0/m or more and 10/m or less, it was judged as pass. When any of these conditions were not satisfied, it was determined as disqualified and described as "C" in the evaluation column in the table. In addition, the core loss Wp of the example judged to be pass was evaluated as S (extremely good), A (more good), and B (good) based on the same criteria as in Example 1.

Tables 3 and 4 show manufacturing conditions, measurement results, and evaluation results of grain-oriented electrical steel sheets. Further, in the example of the present invention, in the component composition of the silicon steel sheet, the total content of S and Se is 0.005% or less, the acid-soluble Al content is 0.01% or less, the N content is 0.005% or less, and the balance is Fe and impurities. was

Referring to the results of Tables 3 and 4, the grain-oriented electrical steel sheet containing Si: 2.5% or more and 4.5% or less, Mn: 0.01% or more and 0.15% or less, in terms of mass%, was evaluated as B or higher (good or higher). Could know. In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 700 ° C./s or more, the iron loss Wp was 0.790 W / kg or less, and the evaluation was A or more (more good). above) was found to be In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 1000 ° C./s or more, the iron loss Wp was 0.785 W / kg or less, and the evaluation was S (extremely good). It was found that Further, in condition B5, since the Si content was too high, hot rolling could not be performed and a grain oriented electrical steel sheet could not be manufactured, it was judged to be disqualified and described as "C (not rolling)" in the evaluation column.

(Example 3)

In terms of mass%, a slab containing C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.024%, acid-soluble Al: 0.03%, N: 0.008%, the remainder containing Fe and impurities, was fabricated. did After heating the slab at 1350°C for 1 hour, hot rolling was performed to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. A cold-rolled steel sheet having a thickness of 0.23 mm was obtained by subjecting the obtained hot-rolled steel sheet to hot-rolled sheet annealing at a maximum temperature of 1100°C for 140 seconds, pickling, and then cold rolling.

Subsequently, the obtained cold-rolled steel sheet was rapidly heated at an average temperature increase rate V (° C./s) shown in Tables 5 and 6, and then subjected to decarburization annealing in a hydrogen atmosphere at 850° C. for 180 seconds. In addition, the temperature increase rate V (°C/s) was taken as the average value of the temperature increase rate in the temperature range of 550 degreeC - 700 degreeC. In addition, in the heating process of the primary recrystallization annealing, the steel sheet tension S (N / mm 2 ), the heating amount T (° C.), and the heating length L (mm) were changed as shown in Tables 5 and 6. The average temperature increase rate V was calculated by the same method as in Example 1.

After applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, finish annealing was performed to obtain a finish annealing sheet, and the finish annealing sheet was washed with water. Thereafter, an insulating film containing aluminum phosphate and colloidal silica as main components is applied to the surface of the final annealing plate, and then baking of the insulating film and flattening annealing for the purpose of flattening the steel sheet are performed so that the sheet thickness is 0.15 mm or more. A grain-oriented electrical steel sheet of 0.23 mm or less was obtained.

Regarding the grain-oriented electrical steel sheet obtained by the above method, the iron loss Wp, the magnetic flux density B8 value, the number of wrinkles having a steepness of 0.01 or more per 1 m in the sheet width direction, the component composition of the silicon steel sheet, and The average particle diameter of secondary recrystallized grains was measured.

When the core loss Wp was 0.800 or less and the wrinkle ratio was 0/m or more and 10/m or less, it was judged as pass. When any of these conditions were not satisfied, it was determined as disqualified and described as "C" in the evaluation column in the table. In addition, the core loss Wp of the example judged to be pass was evaluated as S (extremely good), A (more good), and B (good) based on the same criteria as in Example 1.

Tables 5 and 6 show manufacturing conditions, measurement results, and evaluation results of grain-oriented electrical steel sheets. Further, in the example of the present invention, in the component composition of the silicon steel sheet, the total content of S and Se is 0.005% or less, the acid-soluble Al content is 0.01% or less, the N content is 0.005% or less, and the balance is Fe and impurities. was

Referring to Tables 5 and 6, it can be seen that the grain-oriented electrical steel sheet having an average secondary recrystallized grain diameter of 10 mm or more and 50 mm or less, and a magnetic flux density B8 of 1.930T or more received an evaluation of B or higher (good or higher). there was. In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 700 ° C./s or more, the iron loss Wp was 0.790 W / kg or less, and the evaluation was A or more (more good). above) was found to be In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 1000 ° C./s or more, the iron loss Wp was 0.785 W / kg or less, and the evaluation was S (extremely good). It was found that

(Example 4)

In mass%, C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.005%, Se: 0.019%, acid-soluble Al: 0.03%, N: 0.008%, the balance being Fe and impurities. A slab containing After heating the slab at 1350°C for 1 hour, hot rolling was performed to obtain a hot-rolled steel sheet having a thickness of 2.1 mm. The obtained hot-rolled steel sheet was subjected to hot-rolled sheet annealing in which the obtained hot-rolled steel sheet was annealed at a maximum temperature of 1100°C for 140 seconds, pickled, and then cold-rolled to obtain a cold-rolled steel sheet. In cold rolling, the cumulative reduction ratio was controlled so that the finally obtained grain-oriented electrical steel sheet had the sheet thickness shown in Table 7.

After the obtained cold-rolled steel sheet was rapidly heated so that the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. was 1000 ° C. / s, decarburization annealing was performed at 850 ° C. for 180 seconds in a hydrogen atmosphere. In the heating process of the primary recrystallization annealing, the steel sheet tension S was set to 7.84 N/mm 2 , the heating amount T was set to 400° C., and the heating length L was set to 400 mm. The average temperature increase rate V was calculated in the same manner as in Example 1.

After applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, finish annealing was performed to obtain a finish annealing sheet, and the finish annealing sheet was washed with water. Thereafter, an insulating film containing aluminum phosphate and colloidal silica as main components is applied to the surface of the final annealing plate, and then baking of the insulating film and flattening annealing for the purpose of flattening the steel sheet are performed so that the sheet thickness is 0.15 mm or more. A grain-oriented electrical steel sheet of 0.23 mm or less was obtained.

Regarding the grain-oriented electrical steel sheet obtained by the above method, the iron loss Wp, the magnetic flux density B8 value, the number of wrinkles having a steepness of 0.01 or more per 1 m in the sheet width direction, the component composition of the silicon steel sheet, and The average particle diameter of secondary recrystallized grains was measured.

When the core loss Wp was 0.800 or less and the wrinkle ratio was 0/m or more and 10/m or less, it was judged as pass. When any of these conditions were not satisfied, it was determined as disqualified and described as "C" in the evaluation column in the table. In addition, the core loss Wp of the example judged to be pass was evaluated as S (extremely good), A (more good), and B (good) based on the same criteria as in Example 1.

Table 7 shows the manufacturing conditions, measurement results, and evaluation results of grain-oriented electrical steel sheets. Further, in the example of the present invention, in the component composition of the silicon steel sheet, the total content of S and Se is 0.005% or less, the acid-soluble Al content is 0.01% or less, the N content is 0.005% or less, and the balance is Fe and impurities. was

Referring to Table 7, it was found that the grain-oriented electrical steel sheet having a sheet thickness of 0.15 mm or more and 0.23 mm or less was rated B or higher (good or higher).

(Example 5)

In terms of mass%, a slab was prepared containing C: 0.08%, Si: 3.3%, Mn: 0.08%, S: 0.023%, acid-soluble Al: 0.03%, N: 0.008%, the remainder containing Fe and impurities. did After heating the slab at 1350°C for 1 hour, hot rolling was performed to obtain a hot-rolled steel sheet having a thickness of 2.3 mm. A cold-rolled steel sheet having a thickness of 0.23 mm was obtained by subjecting the obtained hot-rolled steel sheet to hot-rolled sheet annealing at a maximum temperature of 1100°C for 140 seconds, pickling, and then cold rolling.

Subsequently, the obtained cold-rolled steel sheet was rapidly heated at an average temperature increase rate V (°C/s) shown in Table 8 below, and then subjected to decarburization annealing in a hydrogen atmosphere at 850°C for 180 seconds. In addition, the average temperature increase rate V (°C / s) is the average value of the temperature increase rate in the temperature range of 550 ° C to 700, and during the rapid temperature increase of the primary recrystallization annealing, the steel sheet tension of 7.84 N / mm in the sheet-threading direction of the cold-rolled steel sheet granted. In addition, as shown in Table 8 below, the number of heating devices, the heating amount T (℃), and the heating length L (mm) during primary recrystallization annealing, including the heating process in the temperature range of 550 ° C to 700 ° C, changed. The average temperature increase rate V was calculated in the same manner as in Example 1.

After applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, finish annealing was performed to obtain a finish annealing sheet, and the finish annealing sheet was washed with water. Thereafter, an insulating film containing aluminum phosphate and colloidal silica as main components is applied to the surface of the final annealing plate, and then baking of the insulating film and flattening annealing for the purpose of flattening the steel sheet are performed so that the sheet thickness is 0.15 mm or more. A grain-oriented electrical steel sheet of 0.23 mm or less was obtained.

Regarding the grain-oriented electrical steel sheet obtained by the above method, the iron loss Wp, the magnetic flux density B8 value, the number of wrinkles having a steepness of 0.01 or more per 1 m in the sheet width direction, the component composition of the silicon steel sheet, and The average particle diameter of secondary recrystallized grains was measured.

When the core loss Wp was 0.800 or less and the wrinkle ratio was 0/m or more and 10/m or less, it was judged as pass. When any of these conditions were not satisfied, it was determined as disqualified and described as "C" in the evaluation column in the table. In addition, the core loss Wp of the example judged to be pass was evaluated as S (extremely good), A (more good), and B (good) based on the same criteria as in Example 1.

Table 8 shows the manufacturing conditions, measurement results, and evaluation results of grain-oriented electrical steel sheets. Further, in the example of the present invention, in the component composition of the silicon steel sheet, the total content of S and Se is 0.005% or less, the acid-soluble Al content is 0.01% or less, the N content is 0.005% or less, and the balance is Fe and impurities. was

Referring to Table 8, it was found that grain-oriented electrical steel sheets (examples of the present invention) satisfying the conditions stipulated in the present invention were rated B or higher (good or higher). In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 700 ° C./s or more, the iron loss Wp was 0.790 W / kg or less, and the evaluation was A or more (more good). above) was found to be In addition, in the example of the present invention in which the average temperature increase rate V in the temperature range of 550 ° C. to 700 ° C. in the primary recrystallization annealing was 1000 ° C./s or more, the iron loss Wp was 0.785 W / kg or less, and the evaluation was S (extremely good). It was found that

In addition, in the examples of the present invention in Table 8, it was found that the conditions of the present embodiment were satisfied under any conditions regardless of the number of heating devices.

As mentioned above, although preferred embodiment of this invention was described in detail, referring an accompanying drawing, this invention is not limited to these examples. It is clear that those skilled in the art to which the present invention pertains can conceive of various changes or modifications within the scope of the technical idea described in the claims. It is understood to fall within the technical scope of the invention.

According to the above aspect of the present invention, a grain-oriented electrical steel sheet having a better surface shape when heated more rapidly than in the prior art in primary recrystallization annealing and having a reduced iron loss value even without magnetic domain control treatment, and manufacturing thereof method can be provided.

1: grater
10, 21, 22, 31, 32, 41, 42: heating device

Claims (2)

a silicon steel sheet;
A forsterite film disposed on the silicon steel sheet;
A grain-oriented electrical steel sheet having an insulating film disposed on the forsterite film,
The silicon steel sheet has a component composition in mass%,
Si: 2.5% or more and 4.5% or less;
Mn: 0.01% or more and 0.15% or less;
Sum of S and Se: 0% or more and 0.005% or less;
Acid soluble Al: 0% or more and 0.01% or less, and
N: 0% or more and 0.005% or less
and the balance includes Fe and impurities,
The average particle diameter of the secondary recrystallized grains of the silicon steel sheet is 10 mm or more and 50 mm or less,
The grain-oriented electrical steel sheet,
The plate thickness is 0.15 mm or more and 0.23 mm or less,
Iron loss Wp is 0.800 W/kg or less with W _17/50 ,
The presence ratio of wrinkles having a steepness of 0.01 or more is 0/m or more and 10/m or less in the sheet width direction,
A method for producing a grain-oriented electrical steel sheet having a magnetic flux density B8 value of 1.930T or more, and the component composition, in mass%,
C: 0.02% or more and 0.10% or less;
Si: 2.5% or more and 4.5% or less;
Mn: 0.01% or more and 0.15% or less;
Sum of S and Se: 0.001% or more and 0.050% or less;
Acid-soluble Al: 0.01% or more and 0.05% or less;
N: 0.002% or more and 0.015% or less
A step of obtaining a hot-rolled steel sheet by heating a slab containing Fe and impurities, the balance of which contains Fe and impurities, at 1280° C. to 1450° C., and performing hot rolling;
A step of obtaining a cold-rolled steel sheet by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing and then performing cold rolling twice or more with intermediate annealing interposed therebetween;
A step of subjecting the cold-rolled steel sheet to primary recrystallization annealing;
Applying an annealing separator containing MgO to the surface of the cold-rolled steel sheet after primary recrystallization annealing, followed by final annealing to obtain a final annealed sheet;
A step of applying a planarization annealing after applying an insulating film to the final annealing plate,
In the temperature raising process of the primary recrystallization annealing, the average temperature increase rate V (° C./s), which is the average value of the temperature increase rates from the point at which the temperature rise was initiated to the point at which the temperature elevation was terminated, in the temperature elevation process including the temperature rise of 550° C. to 700° C. is 400 ° C / s or more and T / s, which is the ratio of the temperature increase amount T (° C.) of a series of temperature increase processes including temperature rises in the temperature range of 550 ° C. to 700 ° C. and the heating length L (mm) of the series of temperature increase process L (°C/mm) is 0.1 ≤ T/L ≤ 4.0, the tension S (N/mm) applied in the sheet-threading direction of the cold-rolled steel sheet is 1.96 ≤ S ≤ (19.6-1.96 × T/L), and V When ≤1000, the tension S is 1.96≤S≤(25.5-0.0137×V), and when V>1000, the tension S is 1.96≤S≤11.8
Method for producing a grain-oriented electrical steel sheet, characterized in that. a silicon steel sheet;
A forsterite film disposed on the silicon steel sheet;
A grain-oriented electrical steel sheet having an insulating film disposed on the forsterite film,
The silicon steel sheet has a component composition in mass%,
Si: 2.5% or more and 4.5% or less;
Mn: 0.01% or more and 0.15% or less;
Sum of S and Se: 0% or more and 0.005% or less;
Acid soluble Al: 0% or more and 0.01% or less, and
N: 0% or more and 0.005% or less
and the balance includes Fe and impurities,
The average particle diameter of the secondary recrystallized grains of the silicon steel sheet is 10 mm or more and 50 mm or less,
The grain-oriented electrical steel sheet,
The plate thickness is 0.15 mm or more and 0.23 mm or less,
Iron loss Wp is 0.800 W/kg or less with W _17/50 ,
The presence ratio of wrinkles having a steepness of 0.01 or more is 0/m or more and 10/m or less in the sheet width direction,
Magnetic flux density B8 value of 1.930T or more
Grain-oriented electrical steel sheet, characterized in that.

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